Jeff Merkley is trying to accomplish what the failed Oregon GMO labeling measure set out to do. The Democratic senator introduced a bill in the U.S. Senate that would require companies to label whether food contains genetically-engineered ingredients.

Oregon voters were almost evenly split in 2014 on support for Measure 92, one of the first ballot measures in the country to raise the issue of genetically-modified organism labeling. It failed by less than 1,000 votes.

Since then, support for GMO labeling has only increased throughout the country.

"A critical mass of consumers want to know, and we say that's their right to know and we'll put it on the package," Merkley said.

Congress was forced to reckon with the issue when Vermont passed its own GMO labeling measure, which goes into effect July 1. Food companies are suing to stop it from going into effect, saying that a state-by-state approach to labeling laws would be a pain to deal with, maybe even impossible to get right.

"They make a very legitimate point and that point is, my goodness, if we have a whole bunch of states that have a bunch of labeling standards, that just wouldn't work in interstate commerce," Merkley said.

So he, along with Sens. Patrick Leahy, D-Vermont, Jon Tester, D-Montana and Dianne Feinstein, D-California, introduced a bill they call a compromise, that would require mandatory labeling near the ingredients list. The billallows fours options for labeling that require either identifying each GMO ingredient or including a blanket statement that some ingredients are genetically-engineered.

"It's a one-second test. You can pick up the package, and in one second you can know," Merkley said.

He says it is a compromise between consumer groups that want clear, quick labeling and industry groups that don't want GMO labels to scare away customers.

The Democrats' effort follows a heated debate in the U.S. Senate over a food industry-backed bill that would have blocked states from passing labeling laws. It would have also allowed voluntary labeling, crediting companies for small steps like saying their products contain GMOs on social media.

That bill, introduced by Kansas Sen. Pat Roberts, a Republican, died on the Senate floor after clearing the Senate agriculture committee. The opposition to labeling is still strong. Texas Sen. Ted Cruz, running to be the Republican party's presidential candidate, has bashed labeling supporters on the campaign trail, calling them "anti-science zealots."

Many polls find that a majority of Americans support labeling products that contain GMOs. Food industry groups that oppose labeling say that labels carry an inherent negative message that would seem like a warning to customers.

Since Oregon's labeling fight, some companies have started voluntarily labeling their products, sensing the change of tides.

Campbell Soup Company announced in January that all the companies products -- which includes Pepperidge Farm, Prego, Plum Organics and V8 -- will carry labels soon. Mars, the candy company that makes M&Ms, and General Mills both made the same decision in the past month.